some nights ago I soldered the GPIO header to my Pi Zero W. I thought it was a clean job and tried to power it on - didn’t boot. Then tired me noticed too late that some solder had dropped which created a short, on the backside between the Pin 1 and the nearby pad from the SD card module. Powered off again and removed the solder.

It booted fine and all looked good until I noticed the onboard Wifi was not working. And it hasn’t since. Tried different raspian installations, which had worked befored and also clean images. But no luck. There is no Wifi device showing up at all (lsusb, iwconfig, etc., even checked rfkill). External Wifi dongle works instantly. Bluetooth, by the way is still working.